Rivet setting tool



July v15, 1947.` l. A. AMTSBERG l RIVM SETTING Toon INVENTOR 557-5? A ,017555424 ATTORNEY Patented July 15, 1947 I RIVET SETTING TOOL Lester A. Amtsberg, Cleveland, Ohio, assignor to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application December 30, 1941, Serial No. 424,964

r(Cl. 218-19) 19 Claims.

1 This invention relates to tools for setting rivet nuts, which are internally threaded tubular screw anchors mounted in thin sheet metal walls by the riveting-like process of expanding the shank portion inside the wall while ahead portion is pressed against the outer surface of the wall.

Rivet nuts have previously been known |but their use has been restricted because of the lack of a. suitable vtool by which they might be rapidly and eiilciently installed. It is necessary in setting rivet nuts that a threaded working implement or bit be first inserted therein, then rotated to en gage the threads on the bit with the threads in the nut, and finally, when such engagement has been effected, to stop the relative rotary movement and pull the bit outward in a. direction to crimp or collapse the rivet nut shank against an anvil engaging the head thereof. Heretofore, the only implements commercially used for this purpose have been hand operated, requiring separate manual movements for each step'of the installa.- tion. This method does not meet the demands of large scale production and is generally unsatisfactory for the reason that uniformity in the amount of 'set applied to each of a series of rivet nuts cannot be obtained.

It is proposed by this invention to replace the hand actuated crimping tools of the prior art with a power tool which will carry ou't uniform setting operations each in response to a single actuation of the motor control element.

One object of the invention is to broaden the field of use of rivet nuts by providing a power tool for laccomplishing their installation.

Another object is to set rivet nuts by a power tool having as its prime mover a rotary motor.

A further object is to embody in a rotary power tool means for initiating automatically and in the proper sequence the rotating and reciprocating movements of the driven elements necessary to set rivet nuts.

A still further object is to develop a powertool for setting rivet nuts which is simple and rugged in construction and is comparable in size and' manner of handling to screw driving and like tools now in general use.

The carrying out of these objects has resulted -in a tool novel in its front end portion where there is provided a motor driven driving shaft, a work engaging bit, a yielding means tending to rotate the bit in unison with the driving shaft, means operated by pressure of the tool againstA the work for interrupting rotation of the bit, and means responsive to a relative turning movement between the driving shaft and bit for effecting a longitudinalnon-rotating motion of the bit.

A feature of the invention is a reciprocable anvil against which the rivet nut is collapsed and which acts to terminate one step of the operation and initiate a second.

Another feature of the invention is a positive lock preventing rotation of the bit and compelling axial movement thereof during part of the return stroke.

Other features and objects of the invention will be apparent from the following description when read in conjunction with the accompanying drawing, wherein:

Fig. 1 is a view, in longitudinal section, of the front end portion of a tool embodying the present invention,'the tool being shown inactive and positioned for application to the work;

Fig. 2 is a view, similar to Fig. l, showing the tool at the end of a rivet nut setting operation before its withdrawal from the work;

Fig. 3 is a view, in cross-section, taken along the line 3-3 of Fig. 1; and l Fig. 4 is a view, in cross-section, taken along the line 4--4 of Fig. l.

For the sake of convenience the operation of installing the threaded bushings or tubular rivet nuts is sometimes referred to in the specication as "rivet setting, and the elements themselves described as rivets. .Y

. Since the invention is concerned primarily with the work engaging driven elements of the tool it may take the form of an attachment adapted to be fitted to the front end of a rotary tool powered lby a reversible air or electric motor. In this instance, the 'front portion of the tool is removed and replaced with the present attachment, the tool being thus converted from a conventional f portable or pedestal mounted screw driving, nut

running or like machine to a rotary rivet setter. Alternatively, the invention may be permanently embodied in a reversible rotary tool intended solely for the work of setting tubular rivets. In each example, the front end construction of the tool is the same. y

Referring to Figs. 1 and 2 there is provided at the front of the motor cylinder (not shown) a clamp nut I0 fixed to said cylinder. Unrota/tably fixed to the. motor cylinder by the clamp nut and. extending forwardly therethrough is a sleeve Il in which is mounted a bearing I2 for the forward end of a shaft I3. The shaft I3 is geared directly vto the motor and is rotatable in either a right tion means normally effective to transmit rotation from one to the other of the shafts. As shown, the outer end of shaft I3is hollow or tubular in shape and receives the inner end of an operative engagement between the elements causing an axial movement of the driven shaft in response to a relative turning movement of theshafts. Resisting such relative turning movement is a coil spring I1 surrounding the telescoping portions of the shafts I3 and I6 and compressed between respective shoulders I8 and I8 thereon. The spring I1 maintains a comparatively tight frictional engagement between the threaded portions of the driving and driven shafts and, in conjunction with the threads, constitutes a friction clutch connecting the shafts for rotation as the wall is comprised of two sheets .'oined together by the rivet setting'operation, has been sea unit. Should the driven shaft IB, in the course of its rotation, encounter resistance sulcient to overcome the spring I1 the driving shaft lI3 is permitted to rotate relatively to the driven shaft, effecting thereby axial movement of the driven shaft in a forward or rearward direction dependf ing upon the direction of rotation of the driving shaft.

shank of a bit 2I is non-rotatably mounted. The f bit is Aheld in place by conventional means which include a ball 22 carried in a radial opening 23 in the shaft and engageable with a notch 24 in the bit. The ball 22 is held in place by a longibetween an internal shoulder 28 thereon and an annular flange 28 on the shaft maintains the ytudlnally shiftable sleeve 25 encircling the front sleeve in advanced position closing the radial opening 23. To remove the bit 2| the sleeve 25 is pressed rearwardly moving the shoulder 28 out of alignment with opening 23 to permit ball 22 to be cammed out of the notch 24 as the bit is withdrawn.

The bit 2| projects through the open front of housing extension I5 and is threaded at its outer end for engagement with the internal 'threads of the rivet. The rivet or rivet nut, shown at k3| lected merely by way of example since rivet nuts are also mounted in single sheet walls.

The rivet is collapsed against an anvil 34 which is positioned at the front end of the tool and has a forwardly projecting annular abutment 35 surrounding the bit 2| and engageable with the rivet head 3 la. The anvil 34 is co-axially disposed with respect to the bit 2I and has a central bore 36" through which the bit passes. The bore 36 has a polygonal shape and that portion of the bit passing through the bore has a similar shape and has a sliding fit within the bore (see Fig. 4) Consequently, fthe anvil is constrained to rotate with the bit but is movable relatively thereto in an axial direction. A rearwardly extending hub 31 on the anvil is mounted in a thrust bearing 3B. the inner element of which is fixed to hub 31 with the outer element normally resting on an internal flange 39 on housing extension I5 and movable relative thereto. Between the hub 31 and the abutment 35 the anvil 34 has a circular flange providing two shoulders, the inner of which is contacted by the thrust bearing 38 and the outer of which lies just within housingextension I5 in advance of the internal flange 39. Secured to the front of the flange 39 and arranged between the flange and the anvil 34 is a fabric ring 4I which when engaged by the anvil acts as a friction clutch or brake tending to resist rotation of the anvil. The anvil normally is held out of contact with the ring 4I by the yielding pressure of a split ring 42 made of spring steel and interposed between the rear of thrust bearing 38 and a spacing ring '43 which abuts against the front of housing I4.`

There is provided a locking ring 44 fixed in a counterbore 45 in the rear of housing I4. Referring to Fig. 3, the inner surface of locking ring 44 is formed with a series of longitudinal grooves 46 adapted to receive a locking ball 41 mounted w.in a transverse opening 48 in the driven shaft I6.

passed through aligned openings in a pair of sheet metal pieces 32 and 33, is tubular in shape and has its inner surface threaded through approximately one-half its length. 'I'he threads begin near 'the mid-point of the rivet and continue to its outer end or that end opposite the head 3F.

'I'he internal diameter of the rivet 3I is such that the bit 2I may be inserted therein and the rivet operatively connected to the -bit by an initial axial movement of the elements and a subsequent [turning movement as the bit encounters the threads in the rivet. It is the function of the tool,- following such operative engagement, automatically to discontinue rotary motion of the bit and cause `anaxial non-rotating movement thereof in a rearward direction while the reaction of the pulling force and the pressure of the tool body is exerted in a direction tending to prevent the rivet from following the rearward movement of the bit. The effect, as is shown in'Fig. 2, is to collapse that portion of the rivet between the head 3IEL andthe internal threads to form an annular shoulder inside the inner work piece 33, which shoulder complements the head 3Ia in lock tight permanent connection between the sheets 32 and 33. The installation illustrated, in which The ball 41 is pressed radially outward by a spring 49 confined in the opening 48 Ibetween the ball and a sleeve 5 Il mounted on the driven shaft. The sleeve 5I serves also to retain the locking ball 41 within the opening 48 but has a radial opening through which the ball may pro-ject into cooperative relation with the grooves 46 in locking ring 44. The driven shaft I6 normally occupies a position in which the locking ball 41 lies below th'e ring 44 (Fig. 1).

In the operation of the tool the parts retain the position shown in Fig. l While the tool is lightlypressed forwardly during advance of the bit through the tubular rivet. At rthis time driving sleeve I3 and driven shaft I6 rotate as a unit due to the friction between the threads created by the pressure of spring I1. The anvil 34 rotates with the bit as it effects a screw threaded engagement with the stationary rivet and, in the course of such movement, the whole tool is pulled toward the rivet until the anvil contacts the rivet head 3Ia. The forward, but not rotary, motion of the anvil ceases at this point and further rotation of the bit causes advance of the tool and bit relatively to the anvil and therefore is accompanied by advance of ring 43 and consequently by compression of spring 42, and this advance causes the friction ring 4I carried by the housing extension to approach and contact the anvil. Further advance causes vcompression of friction ring 4I and more forceful contact between anvil 34 and head 3l of the rivet whereby the rotary motion of the anvil. and consequently of the bit and the driven, shaft I 6, is slowed and nally stopped, due

to the-braking action of ring 4I on anvil 34. The

driving shaft I3, however, continues to rotate and spring 49, due tothe camming action of the ring 44 on ball 41. As the rivet collapses there is a continued tendency of anvil 34 to slip against the rivet and ring 4I with the attendant tendency of the bit to screw farther into the rivet. Should a little slip in fact occur, ball 41 may be vcarried around until it drops into the first reached groove 46 and thereby supplement the holding force of brake 4I to stop further rotation of the bit into the rivet.l K

The rivet setting movement 'of the bit may be terminated 'by stopping the motor when through observation it is determined that the rivet has kbeen properly set. Preferably, however, the driving shaft I3 is stopped automatically in order that a predetermined extent of movement may be set for the bit. This is best done in the cas'e of a pneumatic tool by regulating the pressure of the air supplied to the motor; while in an electrically powered tool a clutch of predetermined torque head which 'engages a keyway punched in thecapabilities may be interposed between the motor and the driving shaft. Upon completion of the power stroke the parts are in the position shown to Fig. 2 with the housing I4, I5 advanced relative to the bit 2l. To restore the parts to their original condition as shown in Fig. l, it is necessary to retract the housing relative to the bit and also to rotate the bit in a reverse direction thereby freeing it from rivet 3l. v

. To disengage the bit from a collapsed rivet and condition the tool for a new operation it is only necessary to reverse the direction of rotation of the motor and thereby of the driving shaft I3.

' Upon this reversal the reactive forces between the threads of shafts I6 and I3 are released and inaugurated in the opposite direction. The effect of Vthis is for shaft I3 to attempt to rotate shaft I6 with it and thus to rotate bit 2i out of the rivet. However, shaft I6 cannot rotate more than 90 degrees before ball 41 is projected into locking engagement with one of the longitudinal grooves 46 in ring 44 which is Isecured to the housing. As a result .shaft I6 remains stationary and shaft I3 backs away along it. Shaft I3 carries with it housing I4, I5 which first returns flange 39 into contact-with the outer element of the raceway 38 (as in Fig. 1) and thereafter the continued retraction of the housing and thrust'bearing 38 causes anvil 34"Which is attached to the thrust bearing, to back away from the rivet, and thring 44 backs away from ball 41. The locking effect of ball 41 on the driven shaft I6 starts to diminish when the front end of the ring 44 passes beyond the center of the ball, and is finally overcome by the torque transmitted to driven shaft I6 due to the action of spring l I1. Following release, the

driven shaft rotates in the same direction (counterclockwise) as driving shaft I3 and, as soon as it attains the same speed, relative axial movement ceases. After ring 44 has risen t0 disassociate itself from ball41 and while shaft II is getting up to the speed of shaft I3, said shaft I3'backs up a little farther along shaft I3 and thus cames ring 44 above ball 41 to the relationship `shown in Fig. 1. The bltl is turning now in an unscrewing direction with respect to the rivet \threads and so backs 'away from the work until free of the rivet.

It will be noted that the tool of the present attachment is well adapted for' setting rivets whichmust be inserted in the work in an inverted position. This'requires that the rivet be applied first to the tool and then inserted in the, work while mounted on the bit. Many rivets of the kind here disclosed are made with a small key undei the werk sheets. This key prevents the rivet from turning if the threads subsequently are required to receive fastening means, such as a screw or bolt. Holding the rivet in the ngers with the key upwards it is applied to the bit while the bit is turning in a direction which will pull the rivet toward the anvil. When the rivet head contacts the anvil operation of the tool is stopped by closing the motor throttle. -After this contact, sufficient rela,-

. tive axial movement between thetool body and the anvil is provided by spring 42 before the fric- Ition` ring 4I interrupts rotation of the anvil to allow for the motor coasting to a stop and error of judgment in timing the closing of the throttle. .The pressure of spring 42 applied through the anvil to the rivet head holds the rivet firmly and it may easily be guided into the Work with the key and keyway properly engaged. When the rivethead contacts the outer work sheet, the throttle may be opened to further insert the, bit into the rivet and thereby to completely collapse the spring 42, and thereafter to collapse thev rivet against the anvil. l

What' is claimed is:

1. A. rotary tool for upsetting internally threaded tubular rivets, comprising a rotatable driving shaft, a driven shaft, a first friction clutch between said shafts causing said driven 'l shaft normally to turn with said driving shaft,

a threaded bit movable with said driven shaft andadapted to be inserted into said tubular rivet, an

anvil surrounding said bit and adapted to abut against the tubular rivet while said bit advances axially through the rivet and is bperatively engaged therewith, a second friction clutch of which said anvil comprises one element interrupting rotation of said driven shaft and' said bit after a relative axial movement of predetermined extent between said anvil and said bit, said second friction clutch being adapted lto overcome said first friction clutch, and means operable upon the disabling of-said ilrst friction clutch for effecting axial non-rotating movement of said driven shaft A and said bit relative to said anvil.

2. A rotary tool for upsetting internallyl threaded .tubular .rivets,.comprising a rotatable driving shaft, a driven shaft having a telescopic connection wtih said driving shaft, the telescoping portions of said shafts being in threaded en- 'Y gagement to permit a relative axial movement of said shafts when one :is turned relatively to the other, yieldable means normally preventing relative turning movements of said shafts, and means acterized in that said'last named means com 7 prises a brake for said driven shaft having as its cbntrolling element an anvil movable axially of' said driven shaft and engageable with the work to ing portions of said shafts being in threaded enl gagement to permit. a relative axial movement of said shafts when one is turned relatively to the other, a. coil spring surrounding said shafts and compressed between respective abutment means thereon thereby toJ resist relative turning movement of said shafts, and braking means forhalting rotation of said driven shaft against the pressure of said spring to permit a relative turning movement of said driving shaft and agconsequent relative axial movementof said dri-venshaftla 5. A rotary tool for vupsetting internally 4 threaded tubular rivets according to claim 4, characterized in that said braking means includes complementary parts one'of'which is stationary and another of which turns with said driven shaft and is movable longitudinally thereof to-enable and disable said braking means.

6. A' rotary tool for upsetting internally threaded tubular rivets, comprising a rotatable driving shaft,l a driven 'shaft having a telescopic connection with said driving shaft, the telescoping portions of said shafts being in threaded engagement to permit a relative axial movement of said shafts when one is turned relatively to the other, a friction' clutch normally preventing relative turning movements of said shafts,a threaded bit movable with said driven shaft and adapted to be inserted into said tubular rivet, an anvil surrounding said bit and adapted to abut against the tubular rivet while said bit is advanced by the rotation of said driven shaft longitudinally of the anvil into operative engagement with the rivet, and means operated automatically upon a predetermined advance of said bit and upon the rivet being held against rotation to hait rotation of said driven shaft, thereby overcoming said friction clutch to permit an axial movement of said driven shaft and said bit to collapse said rivet against the '1. A rotary tool for upsetting internally threaded tubular rivets, comprising a rotatable driving shaft, a driven shaft havingatelescopic connection with said driving shaft, the telescoping portions of said shafts being in threaded engagement to permit a relative axial movement of said shafts when one is turned relatively to the other,

. spring means resisting relative turning movement of said shafts'a threaded bit secured in said driven shaft in axial alignment therewith and adapted to be inserted into said tubular rivet, an anvil surrounding'A said bit and adapted to=abut against the tubular rivet while said bit is advanced by the rotation of said driven shaft longitudinally of the anvil into operative engagement with the l rivet, and clutch means of which said anvil comprises one element interrupting rotation of said driven shaft and said bit against the pressure of said spring meansy after a relative axial movement of predetermined extent between said anvil and said bit, whereby continued rotation of said driving shaft effects an axial non-rotating move- 'l movement of said driven shaft and said bit in a direction to collapse said rivet against the anvil.

ment' of said driven shaft and bit to collapse said Q `rivet against the anvil.

8. A rotary tool for upsetting internally threaded vtubular rivets, comprising a rotatable driving shaft, a driven shaft having a telescopic connec.

'non with said driving ment to permit a relative` axial movement of said shafts when one is turned'relatively to the other; a ilrst friction clutch normally preventing relative turning movements of said shafts, a threaded bit secured in said driven shaft in axial alignment therewith and adapted to`be inserted into said tubular rivet, an anvil surrounding said bit and4 adapted toA abutagainstthe tubular rivet while said bit is advanced by the rotation of said driven shaft longitudinally of the anvil into operative engagement with the rivet, and a second clutch enabled by the relative longitudinal movement of said anvil and sa'id Jbit for halting rotation of said driven shaft and said bit to permit a turning movement of said driving shaft relative to said driven shaft and a consequent axial non-rotating 9. A rotary tool for upsetting internally threaded tubular rivets-according to claim 8, characterized in that a predetermined torque resistance is set for said first 'clutch by spring means while the resistance of said second clutch varies in response to changes in the relative longitudinal positions of said bit and said anvil from a minimum degree of effectiveness which is less than that set for the rst clutch to a maximum degree of eil'ectiveness which is greater than that set for the first clutch.

10. A. rotary tool for upsetting internally threaded tubular rivets and the like, comprising a housing, a rotatable driving shaft therein, a driven shaft connected to the driving shaft for relative movement which includes an axial anddriven shaft against rotation relative to the housing, thereby increasing the torque delivered by the driving shaft to overcome said yieldable means and cause rearward axial movement of the driven shaft and bit relative to the housing, said braking means acting also for limiting rearward movement of the anvil relative to the housing whereby to hold the rear end of the rivet stationary relative to the anvil while the threaded portion there.. of is pulled rearwardly toward the housing.

1l.v A rotary tool according to claim 10 in which .the braking meansis responsive to rearward movement of the anvil relative to the housing.

12. A rotary tool according to claim 10 in which said braking means is established by the axial pressure of the rivet against the anvil.

l 13. A rotary tool for pulling comprising a housing, a rotatable driving shaft supported therein. a driven shaft exibly coupled to the drvingvshaft by means of a screw-threaded connection, whereby rotation of the driving shaft imparts rotational and axial components of force to the driven shaft, a spring urging the driven shaft forwardly relatively vto the driving shaft to oppose the axial component of force during the power stroke, a bit rigidly connected to the driven shaft and extending `forward beyond the housing, the front end of the bit having a threaded portion for detachable connection with the work,

the torque delivered byl the driving shaft and thereby to cause rearward axial movement of the driven shaft together with the bitin opposition to said spring, said braking means being'established by the axial pressure of the work against the anviland meansfor holding the driven shaft against substantial rotation on reversal of direction of rotation of the driving shaft to permit the bit to move axially forward relative to the anvil to-carry the work/relatively away from the anvil.

14? A rotary tool for pulling comprising a hous- 15 ing, a rotatable driving shaft supported therein, a driven shaft flexibly coupled to the driving shaft by means of a screw-threaded connection, whereby rotation of the driving shaft imparts rotational and axial components of force to the driven shaft,

a spring urging the driven shaft forwardly rela -tively to the driving shaft to oppose the axial conrponent of force during the power stroke, a bit rigidly connected to the driving shaft and ex# tending forward beyond the housing, the front end of the bit having a threaded portion for detachable connection with the work, an anvil adapted -to be interposed between the front end of the housing and the work to hold the rear face of the work, means for interrupting rotation of the driven shaft to increase the torque delivered by the driving shaft and thereby to causerearward axial movement of the driven shaft together with f the bit relative to the housing in opposition to said spring, and holding means established by rearward axial movement of the ydriven shaft'for preventing substantial rotary movement of the driven shaftrelative to the housing, characterized in that said holding means is released only in response to, a predetermined axial movement of the driven shaft forwardly of the housing, whereby n the return stroke the driven shaft and bit are constrained to move forwardly relative tothe housing before they rotate to release the work.'

15. A power tool for installing internally threaded tubular rivet nuts, comprising a bit rotatable into threaded engagement with said rivet nut, an anvil surrounding said bit, said bit being adapted after rotating into engagement with said nut to be drawn inward relatively tosaid anvil to collapse-the nut upon the anvil, a rotary motor, and transmission meansbetween said motor and bit for imparting rotation to said bit and for imparting an axial drawing motion to said bit.

16. A power tool for installing internally threaded ,tubular rivet nuts, comprising a` bit rotatable into threaded engagement with said rivet nut', a rotary motor, a rotatable driving shaft driven by said motor, means normally constraining said bit to turn with said shaft, means acting automatically upon rotation of said bit a predetermined distance into the rivet nut to in. terrupt rotation vof said bit while the shaft continues to turn, and means responsive to relative `rotary movement between said shaft and said blt vz65 to transmit the torque of said motor 'to said bit as anaxial pulling force.

1,7. A power operated tool for upsetting internally threaded tubular rivet nuts and the like comprising a housing, a driving shaft rotatable therein and held against axial movement relative to the housing, a driven shaft connected tothe driving shaft for relative movement which includes an axial and a rotary component, a bit driven shaft and its front end projecting forwardly beyond the housing and threaded for engagement with the threads of the rivet nut, an anvil surrounding the bit and adapted to be interposed between the housing and rivet nut to contact the rear face of the latter, yieldable means resisting relative movement between the drivingand driven shafts to permit thc bit to be driven rotatively intofthreaded engagement the anvil, means operable by the rearward pressure of the rivet nut against the anvil for holding the driven shaft against rotation to initiate rearward movement of the driven shaft relative t0 the hopsing in response to the increased torque delivered by the driving shaft,and a brake operable in response to such initial relative rearward movement of the driven shaft for locking the driven shaft relative to the housing, whereby continued rotation of the driving shaft pulls the driven shaft with axial motion only, together with the bit to upset the'rivet nut.

I 18. A power operated tool for upsetting internally threaded tubular rivet nuts and the like comprising a housing, a ,driving shaft rotatable therein' and held against axial movement relative to thevhousing, a driven shaft connected to the driving shaft for relative movement which includes an axial and a rotary component, a bit 0 having its rear end rigidly connected to the driven shaft and its front end projecting forwardly beyond the housing and threaded for engagement with the threads of the rivet nut, an anvil surrounding the bit and movable axially relative 5 to the housing, yieldable means resisting relative the driven shaft against rotation to initiate rearward movement of the driven shaft relative to the housing inlresponse to the increased torque delivered by the driving shaft, and a second brake operable in response to such initial relative rearward movement of the driven shaft for locking the driven shaft relative'to the housing, whereby continued rotation of the driving shaft pulls the driven shaft with axial motion only, together with the bit to upset the rivet nut.

19. A power operated tool for upsetting internally threaded tubular rivet nuts and the lilrf` comprising a housing, a driving shaft rotatable therein and held against axial movement relative to the housing, a driven shaft connected to the driving shaft for relative movementA which includes an axial and a rotary component, a bit having its rear end rigidly connected to the driven shaft and its front end projecting forwardly beyond the housing and threaded for engagement with the threads of the rivet nutan anvil surrounding the bit and adapted to be interposed between the housing and rivet nut to contact the rear face of the latter, yieldable means resisting relative movement between the vdriving and driven shafts to permit the bit to be driven rotatively into threaded engagement with the rivet nut until the rivet nut abuts against the anvil, means for holding the driven shaft against rotation to initiate rearward movement of the driven having its' rear end rigidly connected tothe 75 shaft relative to the housing, a brake operable with the rivet nut until thelrivet nut abuts against` 2,498,9'56 11 I 12 in response to auch initial relative rearward movement of thev driven shaft for'lockinx the driven shaft relative to the housing. whereby "continued Css cr'rlm The following references arepf record in the rotation of the driving shalt pulls the driven 1 Smmv with um motion only. together wxmtne me m mt bn to upset the rivet nur, md brake hema re- UNITED STATES PA'IIN'IB tained effective upon vreversal of the direction of Number Nm Date rotation o! the drivinl shalt at the end of the 2,283,665 Codden -'..----f f- May 19, 1942 power stroke. whereby to cause the bit to return relatively forwardly before 4ii'. is unscrewed from 10 the rivet nut. and means for automatically disabling the brake upon substantialoompletion ot the forward axial returnfatroke of the bit.

` LESTER A. 

